Fabrication of rGO and g-C₃N₄ co-modified TiO₂ nanotube arrays photoelectrodes with enhanced photocatalytic performance

To enhance the photocatalytic performance of titanium dioxide (TiO₂) and reduce the photocorrosion of graphitic carbon nitride (g-C₃N₄), two-dimensional (2D) reduced graphene oxide (rGO) and g-C₃N₄ co-modified three-dimensional (3D) TiO₂ nanotube arrays (rGO@g-C₃N₄/TNAs) photoelectrodes were fabricated by the combination of impregnation, annealing and electrochemical cathode deposition. The micromorphology and microstructure were observed by SEM and TEM. The crystalline structure and element composition were characterized by XRD, XPS and Raman spectra. The optical and photo-electrochemical properties were analyzed by UV–vis DRS, open circuit potential and photocurrent density. Results indicated that g-C₃N₄ and rGO were successfully loaded on the surface of the TNAs photoelectrodes and formed rGO@g-C₃N₄/TNAs heterostructure. The photocatalytic activity of the photoelectrodes was evaluated by the degradation rate of tetracycline hydrochloride (TC) under xenon lamp irradiation. The introduction of g-C₃N₄ and rGO reduced the band gap of TNAs photoelectrodes and promoted the separation of photo-induced electron-hole pairs. The rGO@g-C₃N₄/TNAs photoelectrodes exhibited higher photo-electrochemical properties and photocatalytic activity. The removal rate of TC by rGO@g-C₃N₄/TNAs photoelectrodes could reach 90% under 120 min photo-degradation and reaction kinetic constant was 2.38 times that of TNAs photoelectrodes. The active radicals capture and ESR experiments results showed that ^[rad]O₂ ⁻ radical and ^[rad]OH radical played the major role in photocatalytic degradation of TC. The possible photocatalytic mechanism of rGO@g-C₃N₄/TNAs photoelectrodes was presented.